William Frederick, Prince of Nassau-Dietz

William Frederick, Prince of Nassau-Dietz (7 August 1613-31 October 1664) was Count of Nassau-Dietz and Stadtholder of Friesland, Groningen, and Drenthe.

Biography
William Frederick, Prince of Nassau-Dietz was the second son of Ernest Casimir I, Count of Nassau-Dietz and Sophia Hedwig of Brunswick-Luneburg. He studied at Leiden University and the University of Groningen, and he served in the Dutch States Army alongside William II of Orange. In 1640, he inherited his brother's estates after he was killed by the Spanish during the Eighty Years' War, and he became Stadtholder of Friesland, Groningen, and Drenthe. William Frederick became an Orangist during the mid-17th century, leading 10,000 troops to put down the States General's coup against William in 1650; he became the de facto regent for the young William of Orange (the future William III of England) after the newborn became stadtholder, and he became an Imperial Prince of the Holy Roman Empire in 1654. During the Second Anglo-Dutch War, he was given command of an army to repel Christoph Bernhard von Galen's invasion of Friesland and Groningen, but he was accidentally shot and killed in 1664.